Validation of the IASI level 2 temperature, humidity, and trace gas products (VALIASI) at Izaña with FTIR high-quality in-situ measurements

Determine empirically the uncertainty of IASI’s level 2 temperature, humidity, and trace gas products (O3, CH4, N2O, CO, CO2) by means of coincident and cloud free IASI and ground-based high-quality Fourier Transform Infrared (FTS) spectrometry at Izaña of atmospheric trace gases. The main results obtained from this validation analysis were published in Sepúlveda et al. (2018), which included PWV from Global Navigation Satellite System (GNSS) and radiosondes (RS92) as secondary references. This work concluded that IASI reproduce well the precipitable water vapor (PWV) variations at the different temporal scale, with a poorer agreement at nighttime and an underestimation of the PWV day-to-day variations and the annual cycle. As a part of the quality assessment, the influence of IASI’s swath angle and AOD on IASI-FTS differences was studied. The results showed no correlation of differences with the different viewing geomtry and a noticeable dependence with the range of aerosol load. This project also showed the consistency between the two IASI instruments aboard the METOP-A and METOP-B, and therefore those observations could be combined as one dataset.

This project will help to improve the EUMETSAT retrieval algorithms thereby reducing the uncertainties in the treatment of these atmospheric components in global climate models.


  • Sepúlveda, E., Report for EUMETSAT Fellowship EUM/VN(14)47: VALIASI: VALidation of IASI level 2 products, EUMETSAT, April, 2018.